Automatic boring grab

ABSTRACT

Automatic boring grab comprising a cylindrical body containing a piston slidingly mounted therein and shovels hingedly linked with the end of said piston, whereas said grab is suspended by a single cable controlled by a hoisting machine and comprises setting means controlling the motion of said piston while closing the said shovels as soon as a pull is exerted on said cable, releasing means controlling the opening of said shovels and actuated by stop means freeing the piston, locking means for locking temporarily the shovels in open position, and automatic means for discharging the cuttings during opening of the shovels.

United States Patent 1,730,704 10/1929 Wild lnventor Pierre Jean-Marie Theodore Allard 178 Blvd. Francois, 1, er, 76 Le Havre, France 4 Appl. No. 26,947 Filed Apr. 9, 1970 Patented Nov. 23, 1971 Priority Apr. 28, 1969 France 6913500 AUTOMATIC BORING GRAB 18 Claims, 24 Drawing Figs.

US. Cl 175/24, 37/183, 175/242 Int. Cl 1366c 3/02 Field 01' Search 175/88, 24, 241,242; 294/1 10; 37/183, 184

References Cited UNITED STATES PATENTS 5/1932 Thornley 175/88 2,910,274 10/1959 Scott 175/242 3,194,329 7/1965 Wallers 37/183 Primary ExaminerJames A. Leppink A ttorney- Kenyon, Kenyon Reilly Carr and Chapin ABSTRACT: Automatic boring grab comprising a cylindrical body containing av piston slidingly mounted therein and shovels hingedly linked with the end of said piston, whereas said grab is suspended by a single cable controlled by a hoisting machine and comprises setting means controlling the motion of said piston while closing the said shovels as soon as a pull is exerted on said cable, releasing means controlling the opening of said shovels and actuated by stop means freeing the piston, locking means for locking temporarily the shovels in open position, and automatic means for discharging the cuttings during opening of the shovels.

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sum 5 or 7 N VE N TOR P/ERQE JEAN-MARIE 7711 00025 A LLARD 1 AUTOMATIC BORING GRAB The present invention has for its object an automatic boring grab adapted to make boreholes in various types of soils. The said boreholes may or may not be tubed and they may be used for instance as foundations or for any other purpose.

Various types of boring grabs are already known, which comprise a cylindrical body containing a piston sliding therein and with the end of which are hingedly linked one or several shovels or shells adapted to excavate or bore the soil. Such grabs were generally suspended by a cable controlled by hoisting means such as a crane or a winch and comprised means controlling the sliding motion of the piston in the cylindrical body so as to cause alternately the opening of the shovels boring the soil and the closing thereof in such a manner as to enable to raise the cuttings out of the borehole.

Such grabs involved a certain number of inconveniences and compelled the user to perform a certain number of more or less complicated handlings which, in particular, slowed down the boring operations. Indeed, the lowering and raising of the grabs were controlled by the cable of a hoisting machine, while the closing of the shovels in the borehole had to be controlled by any other independent means. Similarly, once the grab was extracted from the borehole, it was again necessary to control the opening of the shovels in order that the cuttings contained in the grab be discharged. Such independent shovel control operations were generally carried out by means of a cable.

It is obvious that the emptying operation caused solely by the opening of the shovels or, at the very most, by a slow unwinding of the cable of the hoisting machine was unfavorable to the discharge of the cuttings, especially where the shovels were fouled or contained sticky materials such as soft clay or loamy sand. Such sticky materials were therefore troublesome when the boring operation was repeated and, moreover, they frequently fell back into the borehole.

Furthermore, rough contact of the shovels with the soil to be bored and more particularly with the water, frequently resulted in a parting of the hoisting cable, and this rendered the raising and lowering operations very difficult. On the other hand, the piston was actuated by a complicated pulley-block system occupying the greater part of the grab body, thus rendering the device highly damageable and keeping the same constantly in contact with more or less abrasive cuttings or materials. Since the mechanism driving the piston was complicated, the latter was liable to rapid wear and frequent jamming.

Moreover in certain soils where repeated borings are effected the bottom of the borehole often happens to assume, in the long run, a semispherical shape. The internal wall of the borehole has a tendency to readily become smooth and hard, so that the shells or shovels of the boring grab slide on the said wall and close up without seizing any material. Consequently, when repeated boring operations are performed, a good many of these operations are useless since no material is extracted from the borehole. This results in more rapid wear of the equipment, since it is necessary to carry out a greater number of boring operations than is really necessary.

In order to meet this difficulty, the shovels had therefore to be adapted to be locked temporarily in open position so as to enable the latter to be used really as a tool adapted to dig the soils and to bite the smooth concave ans substantially semispherical wall of the borehole.

Lastly. these known grabs comprise up to the present only two or three shovels, thus making it very difi'lcult to bore cylindrical holes. The verticality of the borehole was practically impossible to ensure, and this entailed the necessity of tubing the borehole.

The present invention has for its purpose to meet all the above-mentioned difficulties and relates to an absolutely automatic boring grab which is extremely simple in use and particularly efiicient in boring any types of soils, in the dry state or in water, even mud-laden water, with or without tubing.

Indeed, the automatic boring grab according to the invention of the type comprising a cylindrical body containing a piston sliding therein and with the end of which are hingedly linked one or several shovels adapted to excavate the soil, the said grab being suspended by a cable controlled by a hoisting device and comprising means controlling the sliding motion of the piston in the cylindrical body and the combined linkage motion of the shovels during the opening and closing thereof, is characterized in that the means controlling the motions of the shovels comprise a setting stud actuated by the impact of the open shovels against the bottom of the borehole and ensuring the closing of the shovels as soon as a pull is exerted on the hoisting cable, releasing means controlling the opening of the shovels and actuated by the impact of the grab, upon completion of its rising motion, against a stop freeing the piston in the said cylindrical body and simultaneously causing the grab to fall down from a given height so as to ensure the uncramming of the cuttings contained in the grab, while a locking member is interposed in the grab body in order to momentarily lock the shovels in open position at the moment of its impact against the earth, and at least one automatic chute discharges the cuttings during the opening of the shovels by being actuated by the downward and upward motions of the grab.

It is thus obvious that the automatic operations ensuring the closing and the opening of the shovels as well as the uncramming and instantaneous discharge of the cuttings during the opening of the shovels impart to the grab of the invention maximum efficiency and great simplicity in operation while at the same time ensuring an excellent regularity in the successive boring operations. Moreover, the discharge operation is connected only with the motion of the grab proper; it is understood that after the uncramming of the cuttings in the shovels, caused simultaneously by the opening of the latter and the rough fall of the grab by gravity from a given height, the sticky materials having thus been readily ejected from the grab may be collected in the aforesaid discharge means in order to be, for instance, subsequently projected far from the borehole. Thus, the falling back of the cuttings into the borehole is completely avoided.

Other objects, characteristics and advantages of the invention will appear as the following description proceeds, with reference to the appended drawings given solely by way of example illustrating one form of embodiment of the invention and wherein:

FIGS. 1, 2, 3 and 4 diagrammatically illustrate the operation of the boring grab during the upward and downward motions thereof;

FIG. 5 is a general elevational view showing the grab hanging from a jib of a hoisting device and ready for use;

FIG. 6 is a longitudinal sectional view upon the line VI-VI of Fig. 8 and shows the grab with its shovels in open position;

FIG. 7 is a sectional view substantially upon the line Vll VII of Fig. 8, in which the shovels (in closed position) are not shown; a

FIG. 8 is a top-side plan view of the grab;

FIGS. 9 and 10 are sectional views upon, respectively, the lines IX-IX and X-X of Fig. 6, illustrating two positions of the locking member;

FIG. 11 is a sectional view, with parts broken away, substantially upon the line Xl-Xl of Fig. 8, wherein the shovels in open position are not shown;

FIG. 12 is a view substantially identical with the previous one, substantially upon the line XIIXII of Fig. 8, wherein the shovels (not shown) are in closed position, and the means controlling the piston carrying the shovels are in a different position as compared to that illustrated in Fig. I 1;

FIG. 13 is an underside plan view of four closed shovels of unequal lengths;

FIG. 14 is an elevational view showing the said shovels in open (continuous lines) and closed (broken lines) positions;

FIG. 15 is an underside plan view showing four shovels of equal lengths in closed position;

FIG. 16 is an elevational view of the said shovels in open (continuous lines) and closed (broken lines) positions;

F 10S. 17 and 18 are perspective views of the setting stud;

FIGS. 19 and 20 diagrammatically illustrate the operating principle of a boring grab equipped with a chute for the discharge of the cuttings, according to one fonn of embodiment ofthe invention;

FIGS. 21 to 24 respectively illustrate the successive steps in the operation of a chute adapted to project the cuttings out of the borehole, according to another fonn of embodiment of the invention.

As shown in Fig. 5, the automatic boring grab according to the invention comprises essentially a substantially cylindrical body 1 at the end of which are mounted one or several hingedly linked shovels 3. The body 1 is hung from thejib 300a or any hoisting machine 300 through the medium of a single cable 17.

Referring more particularly to Figures 6, 7, 11 and 12, it is seen that the body 1 comprises a lower portion lb in which slides a piston 2 carrying a set of shovels 3 hingedly linked with the end of the said piston. The stationary shaft 4 is mounted at the upper portion 1a of the cylindrical body 1. Arranged about this shaft are the means controlling the piston 2, i.e. a drum 5 loosely mounted on a sleeve or spindle 6 which rotates freely on the shaft 4, a gear wheel 7 which is also mounted loosely on the sleeve 6, and a stud 8 carried by a member 9 solid with the sleeve 6.

Chains 10, two in number according to the form of embodiment illustrated, are adapted to wind round the sleeve 6, more precisely in the slots 11 at the ends of the said sleeve, so as to cause a guided and rectilinear sliding motion of the piston 2 in the cylindrical body 1. More specifically, the ends of the chains solid with the sleeve 6 are secured to the latter by suitable means such as a lock 12 (Fig. 7). The ends of the chains connected to the piston 2 are hooked at a fixed point 13 of the cylindrical body 1, thus enabling the chains 10 to wind round a roll 14 rotating on a pin 15 mounted in yokes 16 machined at the upper peripheral portion ofthe piston 2.

The single cable 17 is anchored to the drum 5 through the medium ofa coupling member 18a. in Figs. 7, 11 and 12 it is clearly seen that the cable 17 is guided in the upper portion 1a of the grab body by conventional means 18 forming a chainguide and a pulley 19. The coupling member 180 is mounted on a pin 20 (Figs. 6 and 7) secured in holes 21 forming yokes and provided in the flanges of the drum 5. A ring 22 forming a cable clamp and provided with a clamping screw 23 is mounted on the top wall 111 of the cylindrical body 1, as shown in Fig. 6. Lastly, the cable 17 is removably mounted on the drum 5 and may be secured at will in one of the holes or yokes shown at 5a, 5b, 5c and 5d on the periphery of the drum 5.

A coil spring 24 is secured at its outer end 25 (Fig. 7) to the drum 5 and at its inner end 26 to the sleeve 6, the said spring enabling the drum 5 to resiliently rotate relative to the sleeve 6.

As seen more clearly in Figs. 11 and 12, a gear or ratchet wheel 7 forming a tripping wheel and rotating on the sleeve 6 comprises a substantially arcuate aperture 122. The latter is provided with teeth 121 forming a rack meshing with a pinion 120 mounted at the end of the stud 8. A return spring 124 is mounted between one end 125 of the aperture 122 and a lug 126 solid with the member 9. The spring 124 permanently applies the pinion 120 on an adjusting screw 123 mounted at the end ofthe aperture 122 and projecting into the latter.

As seen clearly in Figs. 6, 17 and 18 the stud 8 is adapted to receive, by its portion 31, a sliding and rotary motion in a housing 32 forming a bearing and provided in the member 9 solid with the sleeve. A spring 33 permanently urges the said stud towards a corresponding cylindrical housing 34 of the drum 5, more precisely in a ball-bearing 35 fitted in the housing 34. The end of the stud 8 has a bevelled shape 36 forming a skew, so that the saidskew readily causes the stud 8 to be disengaged trom the drum 5 by resting upon the ball-bearing 35,

while the remaining portion of the end of the said stud is cylindrical and advantageously causes the stud to be engaged and locked in the housing 34 of the drum 5 constituted by the ballbearing 35.

A rod or the like 38 slidingly mounted with a certain play in the upper portion 111 of the cylindrical body 1 is adapted to be actuated by a ring 39 (Fig. 12), made for instance from cast-iron and supported by chains or cables 40 hanging on the jib of the hoisting machine. A spring 41 retains the rod 38 in its upper position, while an adjustable collar 42 forming a stop limits the travel of the said rod. Lastly, a spring 43 (Figs. 11 and 12) acts upon an arm 127 hingedly mounted at 128 in a substantially vertical position aligned with the rod 38. Thus, during the motion of the rod 38 into one of the notches of the gear wheel 7. the latter, once the tripping is achieved, may complete its rotary travel in the direction ofthe arrow F, (Fig. 12), since the arm 127 hinged at 128 mayjump on the successive teeth of the ratchet wheel 7. The lower end of the am 127 is adapted to readily engage a notch of the ratchet wheel 7 and to this end may be provided with a fork or the like carrying a roll 44 adapted to lodge in one of the said notches. Lastly, there is seen in Fig. 12 a secondary, lower ring 200 hung by means of chains 210 on the tripping ring 39. The secondary ring 200 is adapted to actuate, during its downward and upward motions and by bearing upon the upper wall 111 of the grab body, a chute for automatic discharge of the cuttings, which will be described subsequently.

Referring now more particularly to Figs. 6, 9 and 10, there is seen a device 101 for momentary locking of the piston 2 in the cylindrical body 1. This locking device comprises a cylindrical rod 101 mounted in a bearing 102 secured to the lower portion 1b of the grab body 1 by means ofa bracket 103. The rod 101 is provided at its lower portion with splines, tongues, keys or the like 104 which are for instance diametrically opposed and two in number. The top of the rod 101 is provided with a cam 105 which is for instance keyed on the top of the said rod. The return spring 106 is mounted between the end 107 of the cam 105 and a location 108 on the cylindrical body 1. The rod 101 and the splines 104 thereof may or may not slide into a corresponding hole 109 provided in the upper portion 2a of the piston 2, depending on the angle of the rotation effected by the rod 101 about its vertical axis 1010.

As seen in Figs. 6 and 11 a cam or ramp 110 is mounted on one of the flanges of the drum 5 so as to cooperate with the cam 105 ofthe rod 101 during the rotation of the said drum.

As seen in Figs. 13 to 16, the shovels 3 are preferably four in number. it is obvious that an automatic grab according to the invention may also comprise a smaller or greater number of shovels. The shovels are connected with the piston 2 through the medium oflinks 50 hingedly mounted at 52 (Fig. 6) on the cylindrical body 1 and at 53 on the said links, so that the upwards or downwards motion of the piston 2 controls respectively the closing or the opening of the said shovels.

It should be noted that, as shown in Fig. 6, the piston 2 comprises an inclined internal peripheral portion 54 fonning a recess or undercut, so as to facilitate the downward motion of the sticky cuttings contained in the grab body.

The shovels 3 comprise a pair of opposite shovels 3a and 3c of smaller length, and a pair of opposite shovels 3b and 3d of greater length, as seen in Figs. 13 and 14. Such an arrangement enables to advantageously dig the soil at two different levels during the excavation. On the other hand, Figs. 15 and 16 illustrate another arrangement of the shovels, wherein the four shovels 3 are of equal length.

The upper portion 1a and the lower portion lb of the grab body 1 may be assembled in any suitable manner. ln particular, the upper portion 1a may be provided with a certain number of openings which are particularly advantageous when the boring is carried out in mud-laden water. Thus, the water may escape from the grab body through two openings provided in the upper portion of the latter on either side of a solid portion 111 forming the upper wall of the cylindrical body 1 (FIG. 8).

FIGS. 19 and 20 illustrate the manner in which may automatically take place the discharge of the cuttings contained in the grab body 1. According to the form of embodiment shown in these Figures a chute 74 hinged at 75 on an upright or on the frame of the hoisting machine 300 comprises an arm 73 forming a lever actuated by a cable 72 connected at 77 to another arm which is also hinged at 76 on the hoisting machine 300 and controlled by the upward motions of the grab body 1. A stop 78 limits the travel of the arm 71 under the action of the pull exerted by the return spring 79 which may be secured for instance on an upright of the hoisting machine 300. The chute 74 may be semi-cylindrical in shape so as to be placed above the borehole 70 and allow the cylindrical body of the grab l to pass during its downward motion into the borehole.

Figs. 21 to 24 show a chute 202 according to another form of embodiment, the shape of which is particularly adapted to throw the cuttings proceeding from the grab body 1. Cables 201 are secured by their respective ends to the secondary ring 200 and to the chute at 204, while a return spring 206 connects the point 204 to a fixed point 205 of the hoisting machine 300. Lastly, as appears more clearly from Fig. 5, the chute 202 is hinged at a fixed point 203 of the hoisting machine 300.

The operation of the grab and the means for discharging the cuttings, which have just been described, will be better understood by referring particularly to the diagrams of Figs. 1 to 4.

The single pull and operating cable 17 connecting the hoisting machine 300 with the grab 1 extends initially in a vertical position down to its anchoring position on the drum 5; the user then operates the hoisting machine 300 until the open shovels 3 come into contact with the soil. It is obvious that the length of the chains is at a maximum since the piston 2 is in its lowermost position (Figs. 1 and 6).

Since the shovels 3 are in contact with the soil, the grab body 1 is immobilized but when the cable 17 is slackened it may continue its travel by winding round the drum 5 owing to the fact that the coil spring 24 was previously stretched during the lowering operation already described. This winding of the cable 17 is particularly visible in Figs. 2 and 11. The rotation of the drum 5 therefore takes place under the action of the spring 24 until the stud 8 urged by the spring 33 (Fig. 6) engages the corresponding housing or recess 34 of the drum. This engaging and setting operation renders the drum solid in rotation with the sleeve 6. It should be noted that prior to the slackening of the cable 17 the piston 2 is locked in its lower position in the grab body 1 owing to the locking rod 101. The shovels 3 are therefore locked in open position at the moment of their impact against the soil. On the other hand, as will be described subsequently, the piston 2 is automatically unlocked during the cable winding operation described previously.

The piston 2 thus being unlocked, the user may raise the grab by exerting a pull on the cable 17 which drives the drum 5 solid with the sleeve 6 and causes simultaneously the winding of the chains 10 round the said sleeve and the upward motion of the piston 2 controlling the closing of the shovels on the cuttings. It should be noted that during this stage of winding of the chains the grab body proper is substantially static, and the cable 17 unwinds until it takes a position near the vertical of the said cable, the said position with respect to the vertical being adjustable and limited by the closing of the shovels 3 on themselves and on the cuttings (Fig. 3).

This is the moment when the pull of the single cable 17 acts upon the grab proper so as to cause an upward motion of the cylindrical body 1 until the rod 38 comes into contact with the ring 39 hanging form the jib of the hoisting machine. As appears more clearly from Fig. 12, the end 34 of the rod 38 engages one of the notches of the gear wheel 7. it should be noted that the gear wheel has been driven together with the drum 5 and the sleeve 6 during the upward motion of the piston 2 and the closing of the shovels, described previously, since the pinion 120 of the stud 8 remains constantly engaged in the aperture 122 of the said wheel. Owing to the rod 38 bearing upon the gear wheel 7, the aperture 122 or, more exactly, the rack 121 provided in the said aperture and meshing with the pinion 120 of the stud 8, compels the stud 8 to rotate and ofier its skew portion 36, so that subsequently and under the action of gravity the said stud may easily disengage from the housing or recess 34 of the drum 5. The pinion 120 of the stud 8 may play in the aperture 122 until the said stud completes its motion of simultaneous rotation and retraction in the housing 34. The sleeve 6 is therefore no longer solid with the drum 5, and a reverse simultaneous rotation of the sleeve and the drum takes place and causes respectively and simultaneously the falling of the piston 2 and the opening of the shovels as well as the falling of the grab body 1 proper until the cable 17 returns to the vertical, as clearly shown in Fig. 1. The double impact caused by the rough and simultaneous downward motion of the piston and the grab body results in a very easy freeing of the sticky cuttings which may be contained in the said body. As appears from Fig. 12 illustrating the beginning of the tripping just described, the secondary ring 200 bears upon the top of the grab body and this sets in motion the chute ensuring the discharge of the cuttings.

Of course, the cycle of operations which has just been described may be repeated at will from the moment the cuttings have been discharged and owing to the fact that the shovels are open and the cable 17 is in a vertical position.

It is thus obvious that a single cable ensures the raising and the lowering of the grab as well as the control of the relative motions of rotation of the drum around the sleeve and, therefore, the control of the opening and the closing of the shovels. In addition, since the shaft 4 carrying the various control members is mounted at the upper portion of the grab body, the cuttings contained in the grab have only a slight effect on the said control members and the grab itself may, without any damage, fall into a borehole containing for instance water. at a speed which may reach lO meters per second.

it should also be noted that owing to the means forming the cable clamp (22, 23) the cable 17 can be immobilized. in certain soils in which the borehole may take the shape of a substantially semispherical hole with smooth walls, it is advantageous to be able to immobilize the shovels in open position, since this enables in particular to carry out undercutting and bitting or drilling works.

To this end the locking member 101 operates as follows. When the piston 2 slides towards the bottom of the grab body 1, the said piston slides owing to its opening 109 along the rod 101, down to the lowermost position of the piston shown in Fig. 6 corresponding to the opening of the shovels. During this period of downward motion of the piston 2, the spring 106 (Figs. 9 and 10) between the cam I05 and the grab body 1 is stretched. Thus, as soon as the piston 2 reaches the end of its travel to open the shovels, the splines 104 disengage from the corresponding opening 109 of the piston 2 under the action of the spring 106 causing the rotation of the cam and therefore of the rod 101. Since the splines 104 are no longer in aligned position with the slots of the opening 109 of the piston 2, the latter is locked in lowermost position in the grab body 1 and the shovels 3 at the end of the piston 2 are locked in open position.

As appears more clearly from Fig. 11, by slackening the cable 17 in order that the drum 5 may rotate, the projecting ramp 110 of the drum 5 hits the cam 105, so that the rod 101 and its splines 104 again move into aligned position with the corresponding slots of the opening 109 of the piston 2. It is to be noted that the ramp 110 is shifted by about 90 with respect to the anchoring position of the cable 17 on the drum (Fig. 5 so that when the drum 5 reaches the end of its rotary travel after having effected substantially three-quarters of a complete turn, the ramp 110 is in position A opposite the cam 105. Thus, when the rotary travel of the drum 5 is completed and, therefore, the engaging operation is achieved, the pull exerted on the cable 17 enables the piston 2 to rise in the cylindrical body 1 since the rod 101 has been brought to sliding position as just described.

It should be noted that the said engaging of the stud 8 into the housing 34 may be adjusted very accurately by displacing the screw 123 projecting into the aperture 122 (Figs. 11 and 12).

The discharge of the cuttings collected by the chute 202 (Figs. 21 to 24) takes place as follows: at the end of the upward motion, the upper portion 111 of the grab body 1 raises the ring 200 and causes the stretching of the cables 201 and, therefore, a swinging of the chute 202 under the grab body. When the shovels open, the cuttings fall into the chute 202 (Figs. 22 and 23). Lastly, when the grab body 1 is moved down to carry out a further boring, it drives by its downward motion the secondary ring 200 and therefore causes a slackening of the cable 201, so that the chute 202 withdraws from underneath the grab body to let the latter pass. The chute 202 actuated by the spring 206, while withdrawing, throws the cuttings out of the borehole 70 (Fig. 24). Such a retractable chute prevents the falling of the cuttings back into the borehole and enables to readily carry out repeated boring operations. A rapid and regular boring rate may thus be obtained.

Of course, the invention is by no means limited to the form of embodiment described and illustrated, since the latter has been given by way of example only. Thus, use may be made of any number of chains actuating the piston, any number of shovels hingedly linked with the end of the said piston and any equipment forming the mechanism actuating the chute. The invention therefore comprises all the means constituting technical equivalents to the means described, as well as their combinations, should the latter be carried out according to the spirit ofthe invention.

What is claimed is:

1. In an automatic boring grab comprising a cylindrical body, a hollow piston slidingly mounted in said body, shovels adapted to excavate the soil and hingedly linked to said piston, means for controlling the sliding motion of said piston in said body and a combined linkage motion during the opening and closing of said shovels, and a cable for suspending said boring grab and controlling the latter by means ofa hoisting machine, the improvements consisting in that said means controlling the motion of the piston together with that of said shovels includes setting means actuated by the impact of the open shovels against the soil and enabling the closing ofsaid shovels as soon as a pull is exerted on said cable, releasing means controlling the opening of said shovels, and stop means actuating said releasing means and freeing said piston in said body while simultaneously causing the boring grab to fall down from a determined height so as to ensure the uncramming of the cuttings, whereas said cylindrical body includes locking means in order to momentarily lock said shovels in open position at the moment of their impact upon the soil, and automatic means for discharging said cuttings during the opening of said shovels are provided so as to be actuated by the downward and upward motions of the said cylindrical body.

2. Automatic boring grab as set forth in claim 1, wherein said cylindrical body includes a transversally arranged shaft, a sleeve freely rotating about said shaft, a drum loosely mounted on said sleeve, whereas said cable is anchored to said drum so as to be wound around it, and chains connected to the top end of said piston and adapted to be wound about said sleeve so as to allow the sliding motion ofsaid piston within said body.

3. Automatic boring grab as set forth in claim 2, wherein coil spring means are mounted between said drum and said sleeve. so as to enable said drum to said sleeve.

4. Automatic boring grab as set forth in claim 1, wherein said setting means includes a member solid with said sleeve and a stud adapted to rotate and slide within said member, said stud comprising a bevel shaped end portion adapted to engage one flange of said drum.

5. Automatic boring grab as set forth in claim I, wherein said releasing means includes a toothed wheel adapted to free- I y rotate about said sleeve and rod with spring means mounted on said cylindrical body and acting u n said toothed wheel.

6. Automatic boring grab as set orth in claim 5, wherein said toothed wheel has formed therein a substantially arcuate aperture, which aperture is provided with inwardly projecting teeth therein so as to form a rack meshing, whereas a pinion mounted at the end of the said stud is capable of meshing with said rack meshing.

7. Automatic boring grab as set forth in claim 1, wherein said stop means include a ring supported by said hoisting machine.

8. Automatic boring grab as set forth in claim 1, wherein said locking means comprise a bearing secured to said cylindrical body and a rod mounted therein, said rod including splines and the top of said hollow piston including a hole adapted to engage said splines or not according to the angle of rotation effected by said rod.

9. Automatic boring grab as set forth in claim 8, wherein said rod is provided with a cam, whereas a spring is mounted between said cam and said cylindrical body so as to automatically put said rod out of engagement with said hole.

10. Automatic boring grab as set forth in claim 9, wherein said cam is adapted to cooperate with a ramp integral with one flange of the drum so as to allow said splines to engage said hole when said drum is rotating.

11. Automatic boring grab according to claim 1, wherein said automatic means for discharging the cuttings include a chute, at least a cable for actuating said chute and return spring actuated during the downward and upward motion of said cylindrical body.

12. Automatic boring grab according to claim 11, wherein said cable is actuated by a lever adapted to be continuously pressed upon the top ofsaid cylindrical body by means of said return spring.

13. Automatic boring grab as set forth in claim 11, wherein said cable is connected to a secondary ring supported by said hoisting machine.

14. Automatic boring grab as set forth in claim 2, wherein said drum includes a plurality of holes at its periphery, to which holes the said cable may be removably secured.

15. Automatic boring grab as set forth in claim 5, wherein said rod includes an adjustable collar-shaped stop member so as to limit at will its sliding motion and extends with a hingedly mounted arm adapted to resiliently engage said toothed wheel.

16. Automatic boring grab as set forth in claim 1, wherein said cylindrical body comprises at its top portion clamping means adapted to momentarily immobilize said cable.

17. Automatic boring grab as set forth in claim 1, wherein said hollow piston includes two pairs of opposite shovels having the same length.

18. Automatic boring grab as set forth in claim 1, wherein said hollow piston includes a pair of opposite shovels of smaller length and a pair ofopposite shovels ofgreater length.

resiliently rotate relative to UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, ,9 3 Date; November 23, 97

I Pierre Jean-Marie Theodore Allard It is certified that error appears in the above- :Ldentified patent and that said Letters Patent are hereby corrected as shown below:

In the preamble add the following under the heading "Priority" ---Oot. 22, 1969 France 6936287--- Col. 1, line 6 4, correct the spelling of "and" (second occurrence);

Col. 5, line 69, "form"' should read ---from--- Signed and sealed this 25th day of April 1972.

(SEAL) Attest:

EDWARD M.FLETCI-IER, JR.

Commissionerof Patents M PO-1050 (10-69) USCOMM-DC 50376-P69 uIs. GOVERNMENT rnwrmo orrms 1N9 0-sss-n4 

1. In an automatic boring grab comprising a cylindrical body , a hollow piston slidingly mounted in said body, shovels adapted to excavate the soil and hingedly li nked to said piston, means for controlling the sliding motion of said piston in said body and a combined lin kage motion during the opening and closing of said shovels, and a cable for suspending said boring grab and controlling the latter by means of a hoisting machine, the improvements consisting in t hat said means controlling the motion of the piston together with that of said shovels includes setting means actuated by the impact of the open shovels against the soil and enabling the closing of said shovels as soon as a pull is exerted on said cable, releasing means controlling the opening of s aid shovels, and stop means actuating said releasing means and freeing said piston in said body while simultaneously ca using the boring grab t o fall down from a determined height so as to ensure the uncramming of the cuttings , whereas said cylin drical body includes locking me ans in order to momentarily lock said shovels in open position at the mo ment of their impact upon the soil, and automatic means for discharging said cuttings duri ng the opening of said shovels are provided so as to be actuated by the downward and upward motions of the said cylindrical body.
 2. Automatic boring grab as set forth in claim 1, wherein said cylindrical body includes a transversally arran ged shaft, a sleeve freely rotating about said shaft, a drum lo osely mounted on said sleeve, whereas said cable is anchored to said drum so as to be wound around it, and chains connected to the top end of said piston and adapted to be wound about said sleeve so a s to allow the sliding motion of said piston within said body.
 3. Automatic boring grab as set forth in claim 2, wherein coil spring means are mounted between said drum and said sleeve, so as to enable said drum to resiliently rotate relative to said sleeve.
 4. Automatic boring grab as set forth in claim 1, wherein said setting means includes a member solid with said sleeve and a stud adapte d to rotate and slide within said member, said stud comprising a bevel shaped end portion adapted to engage one flange of said drum.
 5. Automatic boring grab as set forth in claim 1, wherein said releasing means includes a to othed wheel adapted to freely rotate about said sleeve and rod with spring me ans mounted on said cylindrical body and acting upon said to othed wheel.
 6. Automatic boring grab as set forth in c laim 5, wherein said toothed wheel has formed therein a substantially arcuate aperture, which aperture is provided with inwardly projecting teeth therein so as to form a rack meshing, whereas a pinion mounted at the end of the said stud is c apable of meshing with said rack meshing.
 7. Automatic boring grab as set forth in claim 1, wherein said stop means include a ring supported by said hoisting machine.
 8. Automatic boring grab as set forth in claim 1, wherein said locking means comprise a bearing secured to said cylindrical body and a rod mounted therein, said rod including splines and the top of said hollow piston including a ho le adapted to engage said splines or not according to the angle of rotation effected by said rod.
 9. AUtomatic boring grab as set forth in c laim 8, wherein said rod is provided with a cam, wh ereas a spring is mounted between said cam and said cylindrical body so as to automatic ally put said rod out of engagement with said hole.
 10. Automatic boring grab as set forth in claim 9, wherein said cam is adapted to cooperate with a ramp inte gral with one flange of the drum so as to allow said splines to engage said hole when said drum is rotating.
 11. Autom atic boring grab according to claim 1, wherein said automatic means for discharging the cuttings include a chute, at least a cable for actuating said chute and return spring actuated during the downward and upward motion of said cylindrical body.
 12. Automatic boring grab according to claim 11, wherein said cable is actuated by a lever adapted to be continuously pres sed upon the top of said cylindrical body by means of said return spring.
 13. Automatic boring grab as set forth in claim 11, wherein said cable is connected to a secondary r ing supported by said hoisting machine.
 14. Automatic boring grab as set forth in claim 2, wh erein said drum includes a plurality of holes at its peri p hery , to which ho les the said cable may be removably secured.
 15. Automatic boring grab as set forth in claim 5, wherein said rod includes an adjustable collar-shaped stop member so as to limit at will its sliding motion and extends with a hingedly mounted arm adapted to resiliently engage said toothed wheel.
 16. Automatic boring grab as set forth in claim 1, wherein said cylindrical body comprises at its to p portion clamping means adapted to mo mentarily immobilize said cable.
 17. Automatic boring grab as set forth in claim 1, wherein said hollow piston includes two pairs of opposite shovels having the same length.
 18. Automatic boring grab as set forth in claim 1, wherein said hollow piston includes a pair of opposite shovels of smaller length and a pair of opposite shovels of greater length. 